//
// Created by LiuYou on 2021/5/9.
//

#include <cstdio>
#include <cstdlib>
#include <pwd.h>

int main(int argc, char** argv) {

    if (argc < 2) {
        std::fprintf(stderr, "Usage...");
        std::exit(1);
    }

    struct passwd* ptrPasswd = getpwuid(std::atoi(argv[1]));

    std::puts(ptrPasswd->pw_name);

}